Process fob making lignin



Reissued Mar. 30, 1943 PROCESS FOR MAKING LIGNIN Edgar '1. Olson, Pittsburgh. Pa... Raphael Katzen,

chard Mountain. Mich,

of Wisconsin klyn, N. Y., and ,Bi

H. Plow, Iron ascignors to Northwood Chemical Company, Phelps, Wis., a corporation No Drawing. Original No. 2,156,159, dated April 25, 1939, Serial No. 208,499, May 11, 1938. Application for reissue April 25, 1941, Serial No.

ticles which will pass through a mesh, or finer,

screen. These particles are then mixed with dilute sulphuric acid solution, or solutions of like nature which will be known to those skilled in the art, that is, a solution containing between about .4% and about 5% of sulphuric acid, in the ratio of between about 7 parts and about 10 parts of such dilute acid to one part of the finely divided, dry material. This mixture of acid and material is then heated for between about 2 minutes and about 5 minutes at a temperatur between about 165 C. and about 280 C. at a pressure between about 90 pounds and 1000 pounds per .,.square inch.

At the end of the heating period the pressure is reduced to atmosphere pressure. The flash vapors are preferably condensed and the furfural, formic and acetic acids contained therein are recovered. The remainder of the treated material consisting of lignin-cellulose, hexoses, pentoses, wood sugars and water, is filtered to separate the lignin-cellulose materials from the other substances, the latter being subsequently treated and recovered. The lignincellulose materials may be washed, dried, pulverized and then used or sub iected to further treatment.

Lignln cellulose containing material of different sizes'may be treated by the present process. For example, particles'as large as 5 mesh size or even larger may be treated. Particles of 80 mesh size have given satisfactory results but for certain reasons it is advantageous to use even smaller particles. A convenient way to obtain the smaller particles is to grind-the material and then reuuce them in a colloid mill to extremely small particle size. 3

The following examples illustrate various specific conditions under which the' present inven-' tion may be practiced.

Example 1.-Maple wood sawdust or flour was reduced to particles of a size which would pass thru an 80 inch mesh, or finer, screen. This material was then mixed with a 1% sulphuric acid Claims. (01. 260l24) sawdust. This mixture was heated for about 2 minutes at a temperature oi about 180 C. under a pressure of about 150 pounds per square inch. A partially hydrolyzed wood was obtained containing between and of lignin and between 35% and 40% of cellulose.

Example 2.Maple wood sawdust or flour was reduced to particle sizes which would pass thru an 80 mesh, or finer, screen and was then mixed with a 5% sulphuric acidsolution in the ratio of 10 parts of such acid to 1 part of the dried wood substance contained in such sawdust. Thisamixture was heated for about 2 minutes at a temperature of about 220 C. under a pressure of about 325 pounds per square inch. The wood was obtamed from this treatment containing between about and of lignin and between about 20% and 25% of cellulose.

Example 3.Maple wood sawdust or wood flour of a size which passed thru an 80 mesh, or finer, screen was mixed with a 5% sulphuric acid solution'in the ratio of 10 parts 01 the acid to 1 part of the dry wood substance contained in the sawdust. This mixture was heated at a temperature of about 280 C. under a pressure of between 800 and 1000 pounds per square inch for between about 2 minutes and about 5 minutes. The wood material obtained from this, treatment contained between and of lignin and between 5% and 10% of humic acids and cellulose.

In general, other hard and soft woods, corn stalks, straw, bagasse and other lignin-cellulose compounds give results comparable to those of Examples 1 to 3, when similarly treated.

In general, an increase in the strengthgof the sulphuric acid solution decreases the time required for hydrolysis and likewise as the temperature and pressure increase the time of hydrolysis decreases. The iignin content varies directly with the degree of hydrolysis.

It will be understood that the heating step above described may be carried out by simple apparatus. An apparatus which has been used satisfactorily consisted of a metal tube through which the mixture to be treated was moved by a pump of conventional form capable of exerting the desired pressure on the contents. of the tube.

The tube was provided with an automatic pressolution in the ratio of 10 parts of such acid to 1 part of the dry wood substance contained in the sure-release valve at the discharge end which permitted the discharge of the treated material at the predetermined pressure. The tube and its contents were heated to the desired temperature by passing the tube through an oil bath heated to the requisite temperature or by using other suitable heating means. The temperatures ireierred to in the specification and claims are the temperatures measured by thermometers placed in the oil bath.

Having thus described the present invention so that others may be able to understand and practice the same, we state that what we desire to secure by Letters Patent is defined in what is claimed.

We claim:

1. The process of making lignin which comprises the steps of mixing finely divided lignincellulose containing material with a dilute solution oi sulphuric acid, containing between about .4% and about 5% of sulphuric acid, in the ratio from about 7 parts to about 10 parts of such acid to about 1 part of the dry substance, heating such mixture to between about 165 C. and about 280 C. under pressure between about 90 and about 1000 pounds per square inch for between about two and about five minutes, and reducing the pressure to atmospheric.

2. The process of making lignin which cornprises the steps of mixing finely divided lignincellulose containing material with a dilute solution of sulphuric acid, containing between about 1%and about 5% of sulphuric acid, in the ratio from about 7 parts 01' such acid to about 1 part 01' the dry substance, heating such mixture to besures varying with the temperature and ranging between about 90 and about 1000 pounds per square inch for between about two and about five minutes, reducing the pressure to atmospheric,,

removing the vapors and recovering the lignin by filtration.

3. The process of making lignin which comprises ,the steps of mixing finely divided 1ignin-,

tween about 165 C. and about 280 C. under prespressures between about 90 pounds and about 1000 pounds per square inch, varying with the temperature, for between about two and about five minutes, and recovering the lignin by separation of the liquid therefrom.

4. The process or making lignin which comprises the steps of mixing lignin-cellulose containing material, with several times as many parts of a dilute solution of sulphuric acid, heating such mixture to a temperature ranging from about 165 C. upwardly with the pressure,-and subjecting such mixture during such heating to a pressure ranging between about and about 1000 pounds per square inch for between about two and about five minutes, and reducing the pressure to atmospheric and recovering the lignin by known methods. V

5. The process of making lignin which comprises the steps of mixing finely divided ligninceliulose containing material with several times as many parts of a. dilute solution of sulphuric acid, heating such mixture to about 165 C. under a pressure 01' about 90 pounds per square inch for between about two and about five minutes, reducing the pressure to atmospheric and recovering the lignin by known methods.

6. The process of making lignin which comprises the steps of mixing finely divided lignincellulose containing material with several times as many parts of dilute sulphuric acid and continuously passing such mixture through a chamber in which the mixture is heated to between about 165 C. and about 280 C. under pressures ranging betweenabout 90 pounds and about 1000 pounds per square inch for between about two and about five minutes, continuously discharging from said chamber the .thus treated mixture.

7. The process of making lignin which comprises the steps of mixing finely divided lignincellulose containing material with several times as many parts of dilute sulphuric acid and continuously passing such mixture through a chamber in which the mixture is heated to between about 165 C. and about 280 C. under pressure ranging between'about 90 pounds and about 1000 pounds per square inch, continuing such heating until from about 50% to about of the lignincellulose containing material has been hydrolyzed, continuously discharging the thus treated mixture from said chamber, and recovering the lignin by known methods.

EDGAR T. OLSON.

RAPHAEL KA'IZEN.

RICHARD H. PLOW. 

